This application claims the priority of German Patent Application No. 197 35 720.2, filed Aug. 18, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a process for recognizing the ignition cycle of a certain cylinder during the start of an internal-combustion engine in a motor vehicle and, more particularly, to a process using a crankshaft angle sensor which interacts with a crankshaft generator gear equipped with teeth and a reference mark, a camshaft angle sensor for differentiating between the ignition cycle and the exhaust cycle of the cylinders, and an electronic control unit.
Such a process is described, for example, in the chapter entitled "Rotational Speed, Crankshaft and Camshaft Position" of the technical manual "Autoelectric System, Autoelectronic System on the Otto Engine" of the firm Bosch, VDI Publishers, 1994, Pages 224, et seq. This known process is carried out by means of a crankshaft angle sensor (rotational speed sensor), by means of a camshaft angle sensor (Hall sensor) and by means of an electronic control unit (Motronic). The crankshaft angle sensor interacts with a generator gear which is mounted on the crankshaft and is equipped with a plurality of teeth, and includes small tooth gaps as well as one large tooth gap. In the control unit, the signal of the crankshaft angle sensor is converted to a square wave voltage with a constant amplitude. In this case, a high level corresponds to a tooth and a low level corresponds to a tooth gap. For determining the angular position of the internal-combustion engine, the edge distances of the square wave voltage are analyzed. The large tooth gap is assigned to a defined crankshaft position of cylinder one.
The basis of the known process as well as that of the invention is a four-cycle internal-combustion engine. The cylinders of a four-cycle internal-combustion engine are offset with respect to one another such that, after two crankshaft rotations, cylinder one will start the operating cycle again. The piston position of a cylinder is used as the measurable variable for determining the ignition point in time. The pistons of all cylinders are connected with the crankshaft via connecting rods. The crankshaft angle sensor therefore also supplies the information concerning the piston position of all cylinders.
The camshaft controls the inlet valves and the outlet valves of the engine. It therefore rotates half as fast as the crankshaft. When a piston moves to the upper (top )dead center (UDC) position (which corresponds, for example, to the large tooth gap for cylinder one), the camshaft determines whether the cylinder is in the ignition cycle or in the exhaust cycle by the position of the inlet and outlet valves. This information cannot be obtained from the crankshaft position alone. Even if the point in time of the injection is individually adapted for each cylinder (sequential injection), the information concerning the camshaft position is required.
In the case of the known process for recognizing the ignition cycle of cylinder one, the control unit examines whether, during the passing of the (large) generator gear tooth gap, the signal of the camshaft angle sensor has a high or a low level. In the following, the large tooth gap will be called the reference mark.
In the case of the known process, for recognizing the ignition cycle of a certain cylinder for the synchronization of the ignition and/or the injection, during the start of the internal-combustion engine, almost two crankshaft rotations may be required. This delays the starting time of an internal-combustion engine because until the synchronization, no angle-synchronous emission of the ignition and/or injection is possible.
It is therefore an object of the present invention to achieve synchronization of the crankshaft-angle-synchronous events (ignition and injection) as fast as possible.
This object is achieved by a process and arrangement for recognizing the ignition cycle of a certain cylinder during the start of an internal-combustion engine in motor vehicles using a crankshaft angle sensor which interacts with a crankshaft generator gear equipped with teeth and a reference mark, a camshaft angle sensor for differentiating between the ignition cycle and the exhaust cycle of the cylinders, and an electronic control unit. The high and the low levels as well as the descending and ascending edges of the signal of the camshaft angle sensor are analyzed in the control unit and are related to the signal of the crankshaft sensor to recognize the ignition cycle. In the arrangement, the camshaft generator gear is a half-segment disk and is arranged relative to the crankshaft generator gear such that the descending and the ascending edge of the signal of the camshaft sensor each occur at least approximately after half a crankshaft rotation starting with the reference mark of the crankshaft generator gear.
The process according to the invention and the arrangement according to the invention permit a clear synchronization after maximally half a crankshaft rotation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.